Introduction To Blockchain
what is Blockchain
Basically there are n no of blocks and all of them are connected with each other

Actual Definition : A blockchain is a distributed immutable ledger (ledger : a place where transaction information is recorded and the information is immutable and cannot be changed once it is recorded)

Each block of a blockchain contains some data , hash of that block and hash of it's previous block. Data stored in block depends on blockchain.
The first block of any blockchain is called a Genesis block.

why blockchain is distributed ? Blockchain is actually distributed all over the network every node/computer of network has the copy of that blockchain

how the distribution of immutable ledgers takes place
Now consider host 'A' as a miner ( A person who mines a particular block and creates a particular block )
Now A mines a block and added that block to the existing blockchain, once he has completed then he transfer the information of block chain to all the nodes/hosts which are connected to same network after verifying and validating the newly added block all other hosts also include that newly added block to their blockchain.

For instance, Wikipedia is a type of blockchain. The data on Wikipedia is not written by a single person. The information is added and written by various users across different locations and the information added on the Wikipedia page is verified by all the writers of that particular page and then it is validated and added to the page.

1. blockchain cannot be corrupted
Each block in the blockchain is linked to the previous block by storing the cryptographic hash function of the parent block. Hence if there is data tamper in any block, there will be a change in the hash in all the subsequent blocks. This way, any user will easily identify tampering at any point of the ledger without having to check each and every block. If anyone wants to tamper with the blockchain data then one would have to make changes in all the other blocks as well without being noticed. This way, blockchain cannot be corrupted.

2. blockchain is decentralized
Blockchain is designed in a way that it is distributed and synchronized across networks. This way it is not centrally governed or operated by any single organization. It can be run by a group of users privately connected through LAN or run across with thousands of users over the internet. Every user is informed about the creation of new blocks in the ledger.

3. Blockchain works on consensus
To execute any transaction or add information to the blockchain, it is necessary to have validation from all other nodes and after the agreement of all, the new block is added or the transaction is completed. There may be millions of nodes and they might not trust each other, but they trust the algorithms of the system. It works like a voting system. With the ‘consensus’ system, there are no chances of frauds and it helps keep the data most accurate